February 24, 2024

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COVID-19 Vaccine Comparison

COVID-19 Vaccine Comparison

COVID-19 Vaccine Comparison. Currently, five COVID-19 vaccines in China have entered phase III clinical trials. However, because China’s epidemic prevention and control has been so successful, the Phase III trial of China’s COVID-19 vaccine must be done abroad-because in accordance with regulations, the Phase III trial must be conducted in an epidemic area.

Specifically, China’s five vaccines entering Phase III clinical trials have relatively conservative technical routes, all of which are inactivated vaccines or genetically engineered vaccines, while the technical routes of Pfizer and Moderna in the United States are more radical and boldly choose the latest “nucleic acid vaccine”.

COVID-19 Inactivated Vaccines 

Advantages and disadvantages of inactivated vaccines

SINOPHARM (China)’s COVID-19 vaccine and Kexing Biotech‘s “Kierlaifu” belong to “inactivated vaccines.”

COVID-19 Vaccine Comparison

In order to produce these inactivated vaccines, scientists need to cultivate virus strains on suitable cells like farmers’ uncles, and then select the virus with a higher titer that best represents the characteristics of the virus’s antigens to build a large “Virus seed bank” for production preparation.

With the current industrial production capacity in China, there is no need to worry about the production process.

The main pain point of inactivated vaccines is production capacity:

According to the requirements of relevant laws and regulations, the cultivation of live viruses must be carried out in P3 level laboratories.

The monthly production capacity of inactivated vaccines is estimated to be 20 million, and the annual output is 200 million. Serving a small country is nothing, but for China with a population of 1.4 billion, the capacity of 200 million units is theoretically a drop in the bucket.

In terms of effectiveness, according to the information disclosed by Sinopharm Group: A total of 56,000 people have travelled abroad after being vaccinated with the COVID-19 inactivated vaccine, and no one has reported infection.

As the most classic vaccine technology route, there are countless documents, data, and test records related to inactivated vaccines. Relying on the rich experience of predecessors and our own excellent technology, the success of this vaccine is completely “expected”.

It is easy to develop and has good effects, and it can be considered a very reliable vaccine.

However, it should be noted that no one is infected, and not all of them are due to the vaccine. The Chinese habit of wearing masks and washing hands frequently has also played a big role. Moreover, the inactivated vaccine dose is very large each time, but it can only maintain immunity for a short time. It is very practical as an emergency protection for frontline workers, but it is probably not suitable for universal vaccination.

Therefore, although it is true that no one has been infected, academically speaking, the effectiveness of the inactivated COVID-19 vaccine produced in China cannot be determined to be 100%. After all, perceptual life experience is completely different from the calculation standards used in the rational and rigorous academic world.

Advantages and disadvantages of COVID-19 recombinant vaccine (adenovirus vector)

The “Recombinant Novel Coronavirus Vaccine (Adenovirus Vector)” developed by Academician Chen Wei of the Chinese Academy of Military Sciences is a genetic engineering vaccine. Like inactivated vaccines, propagation cells are also needed to cultivate virus strains. Therefore, production capacity will also face a few obstacles.

The advantage of the adenovirus vector vaccine is that Academician Chen Wei’s team has been studying this vector for many years, and has experience in the research of “Ebola vaccine” based on this vector. It can be said that it is easy to get started.

In addition, the adenovirus has a strong ability to infect almost any cell in the body, and its immunogenicity is theoretically very good. Not only can it carry out “humoral immunity” and “neutralizing immunity” in body fluids like ordinary vaccines, but it can also provide protection at the cellular level-equivalent to a body armor for every cell.

The trouble with adenovirus vector vaccines lies in its efficacy and adverse reactions.

Studies in other countries have found that high-dose injections of adenovirus may integrate into human DNA, which is equivalent to genetically modified living people. Although this allows the body to produce more antibodies against the virus, it will increase the risk of cancer in the long run.

In order to avoid such bad side effects, the Chinese scientific research team “castrated” the adenovirus-what was injected into the human body was a “replication-deficient virus” that cannot replicate twice.

Still safe, but the number of antibodies produced has plummeted.

In addition, adenovirus vaccines also face the problem of “pre-existing immunity”-because adenovirus is so common, almost everyone has been infected, which means that everyone has an “antibody weapon” against adenovirus.

When the adenovirus vaccine enters the human body to support the fight against the epidemic, the human immune system will beat up the adenovirus from afar, regardless of the number of conditions.

▲Vaccines can effectively induce antibody production but also have strong adverse reactions

According to experimental data: In each experimental group, about half of the volunteers themselves have extremely high adenovirus antibodies. After vaccination with the adenovirus vector COVID-19 vaccine, the most rapid rise is the antibody against the adenovirus itself, and the “manufacturing” of the COVID-19 virus’s antibody will be suppressed by the adenovirus antibody.

Before vaccination, 20 (56%) participants in the low dose group, 19 (53%) participants in the middle dose group, and 16 (44%) participants in the high dose group had a high pre-existing Ad5 neutralising antibody titre (>1:200). Only five (25%) participants of 20 in the low dose group, seven (37%) participants of 19 in the middle dose group, and ten (63%) participants of 16 in the high dose group, who had high pre-existing Ad5 immunity, had at least a four-fold increase in neutralising antibody titre at day 28 post-vaccination (appendix pp 8–10). Multivariable analysis showed that high pre-existing Ad5 neutralising antibody titres compromised the seroconversion of neutralising antibody post-vaccination, regardless of the vaccine doses, and recipients aged 45–60 years seemed to have lower seroconversion of neutralising antibody compared with the younger reci-pients (Appendix p 11). The Ad5 neutralising anti bodies were significantly boosted post-vaccination (appendix p 12). 

( from “The Lancet” magazine. Safety, tolerability, and immunogenicity of a recombinant adenovirus type-5 vectored COVID-19 vaccine: a dose-escalation, open-label, non-randomised, first-in-human trial )

The other is to bring some adverse reactions to the vaccinators: In the first phase of clinical trials, 54% of people felt pain at the injection site after vaccination, 46% had fever, and 44% felt tired and weak. 39% of people have headaches. . . . . . However, the aforementioned adverse reactions will soon disappear, and most people will return to normal the next day.

Advantages and disadvantages of Pfizer mRNA vaccines

The mRNA vaccines of Pfizer and Moderna are the third generation vaccines.

Since the manufacture of mRNA vaccines does not require culturing cells and harvesting virus strains, as long as the gene sequence is obtained, the reverse development of “antigen proteins” can be started immediately, so the advantage of mRNA vaccines lies in its ultra-fast development and production speed.

Pfizer of the United States claims to be able to produce one billion vaccines a year. Not to mention that the population of 300 million people in the United States is enough to protect a population superpower like China.

 Another advantage of Pfizer vaccine is its super “antibody productivity”-ordinary vaccines are like teachers, inducing cells to produce antibodies. The mRNA vaccine is a “ghost upper body” that directly possesses the soul and directs cells to produce antibodies.

The GMT of neutralizing antibodies in the blood of recovered COVID-19 patients is around 90. Plasma with this level is enough to be used as a treatment method. Among Pfizer vaccinators, the GMT of young people can reach more than three times that of recovered patients. The elderly can also reach 1.6 times.

The highest neutralization titers were measured in samples obtained on day 28 (i.e., 7 days after the second dose) or on day 35 (i.e., 14 days after the second dose). Similar trends were observed for the 50% and 90% neutralizing titers (Fig. S4). The 50% neutralizing GMTs for the two vaccine candidates at the 30-μg dose level on day 28 or day 35 ranged from 1.7 to 4.6 times the GMT of the convalescent serum panel among participants 18 to 55 years of age and from 1.1 to 2.2 times the GMT of the convalescent serum panel among those 65 to 85 years of age. With 10 to 12 valid results per assay from samples that could be evaluated for each group at each time point, pair-wise comparisons are subject to error and have no clear interpretation. 

   (from “New England Journal of Medicine”: Safety and Immunogenicity of Two RNA-Based Covid-19 Vaccine Candidates)

But the problem with Pfizer vaccine is also big: before this, no nucleic acid vaccine has been put into actual use. Without this epidemic, people would not have much knowledge about the immunity of nucleic acid vaccines, and Pfizer vaccine would basically have no precedent worth learning.

mRNA vaccine dose, vaccination frequency, contraindications, and adverse reactions. . . . . . These important information, human scientists are almost blank.

In addition, mRNA is too fragile, unstable in nature, and extremely easy to decompose. mRNA has extremely high requirements for transportation and storage. It needs to be kept at a low temperature of -70℃ during transportation. It has a shelf life of only 5 days in a general hospital refrigerated box. Even with the protection of a large molecular shell, it is very easy to be affected by the human body. Cell lysis.

Although some scientists have stated that they can modify some genes to keep the mRNA vaccine at -20 degrees for 6 months, there is no news of a successful breakthrough.

(Sources: Translated from Sina article)